EBERSWALDE DELTA IN MARGARITIFER TERRA
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ROSS IRWIN SMITHSONIAN INSTITUTION
VALLEY NETWORKS AND PROMINENT DEPOSITS
Hynek et al. (2010), JGR
Wilson et al. (2013), LPSC VALLEY NETWORKS AND PROMINENT DEPOSITS
Mask from Golombek and Grant, this meeting REGIONAL CONTEXT
U: Uzboi Vallis
Ladon L: Ladon Valles
M: Morava Valles
h: Holden crater
e: Eberswalde crater Holden o: Ostrov crater
Ladon and Holden impact basin rings are dashed
ULM S YSTEM DOWNSTREAM
U: Uzboi Vallis
L: Ladon Valles
M: Morava Valles
A: Ares Vallis
White: -1880 m. Red: -2000 m
Irwin and Grant (2009) in Burr et al. (2009) eds., Megaflooding on Earth and Mars DISSECTED CRATERS SUPERIMPOSED ON HOLDEN
Shown here See Grant and Wilson (2012) & Irwin et al., submitted 20 km D = 2.4 km 1 km 250 m D = 2.4 km D = 7 km
D = 12 km
15 km 3 km D = 12 km D = 7 km
3 km 20 km
15 Mosaic: Malin Space Science Systems (lake shade added) 10 km MAJOR LOBES
Late transportive paleochannels
Mosaic: Malin Space Science Systems MEANDERS
Mosaic: Malin Space Science Systems MEANDERS
Songhua River, China (Google) EBERSWALDE CRATER PALEOHYDROLOGY
Eberswalde meander dimensions (m) Paleo- Width Wavelength Arc distance Belt width Radius of λ B channel (mean of 5) m (mean of 2) curvature W λ b a (mean of 3) R c North 130 1240 1140 1000 260 South 50 740 530 420 170
Measured and expected channel width based on meander dimensions (m)
Paleo- Measured Width, from Width, from Width, from Width, from channel width wavelength arc distance belt width radius of (mean of 5) curvature
North 130 100 120 130 100 South 50 60 60 60 70
W λ 0.89 W λ 0.89 W B0.89 W R 0.89 Williams b = 0.17 m b = 0.23 a b = 0.27 b = 0.71 c ( , 1986) Topographic Watershed
-1350 m
Dissected Watershed
Internal Watershed
-1400 m EBERSWALDE CRATER PALEOHYDROLOGY
Width-wavelength relationships in two inverted paleochannels Consistent with meandering rivers on Earth Inverted channels are well-preserved here
Bank-full flow for inverted paleochannels From width: 450 m 3/s (north), 140 m 3/s (south) From wavelength: 400 m 3/s (north), 180 m 3/s (south)
Annual runoff (lake levels of –1350 and –1400 m, 5,000 km 2 watershed) For evaporation of 1 m/y: 8–16 cm/y For evaporation of 0.1 m/y: 0.8–1.6 cm/y
Deposition timescale (deposit volume of 6 km 3) For water/sediment volume ratio of 1,000: tens to hundreds of thousands of years For water/sediment volume ratio of 10,000: hundreds of thousands to millions of yrs Rice et al. (2013) McKeown and Rice (2011) McKeown and Rice (2011)
CONCLUSIONS , 1 OF 2
Eberswalde postdates Holden basin (MN), predates Holden crater (H) Muting of relief continued after Holden impact Fresh craters formed on Holden rim & secondaries, later dissection Eberswalde delta northwest lobe formed first, then eastern lobes If it’s an alluvial fan, then it’s not due to the Holden impact Late transition from distributive to transportive planform Meandering possibly enabled by cementation Paleochannel width consistent with meander geometry Dominant discharge about 400 and 200 m 3/s in two late paleochannels Event runoff production up to 1 cm/day Annual runoff production (intermittent) about 1-20 cm/year Annual snowmelt or infrequent moderate rainfall are possible Deposition timescale 10 4-10 6 years for water/sed volume of 1,000 – 10,000 Abundant outcrops in MSL ellipse, almost all under water CONCLUSIONS , 2 OF 2
Very short deposition time scales are implausible Can concentrate, preserve, and exhume organics (if present) Diverse materials in Holden ejecta, but not in place Date the Holden impact? Site thoroughly mapped and vetted for MSL Low elevation provides margin REFS: Malin and Edgett (2003), Moore et al. (2003), Jerolmack et al. (2004), Bhattacharya et al. (2005), Lewis and Aharonson (2006), Wood (2006), Pondrelli et al. (2008, 2011), Rice et al. (2011, 2013), Mangold et al. (2012), papers by J. Grant and T. Parker